The present invention relates to systems and methods for providing spinal implants, for example, to be used in connection with spinal fusion.
Spinal fusion is a surgical procedure that fuses two or more vertebrae together using bone graft materials supplemented with devices. Spinal fusion may be performed for the treatment of chronic neck and/or back pain, trauma, and neoplasms. Spinal fusion can be used to stabilize and eliminate motion of vertebrae segments that may be unstable, or move in an abnormal way, that can lead to discomfort and pain. Spinal fusion may be performed to treat injuries to the vertebrae, degeneration of spinal discs, abnormal spinal curvature, and/or a weak or unstable spine.
Spinal fusion generally requires a graft material, usually bone material, to fuse the vertebrae together. The bone graft material can be placed over the spine to fuse adjacent vertebrae together. Alternatively, a device (i.e. cage) may be positioned between the vertebrae being fused and filled with the bone graft material. Such a cage can include holes that allow the vertebrae and the graft material to grow together to provide fusion, with the cage supporting the weight of the vertebrae while the fusion is occurring. Most of these cages are limited to only a few cubic centimeters of bone graft material thus limiting the fusion area achieved. Because the fusion mass is under pressure, fusion can be promoted. The disc space height can be restored, taking pressure off of the nerves. The spine alignment, foraminal height, and canal diameter can be restored. In some cases the graft can be placed with minimal disruption of muscles and ligaments using minimally invasive approaches to the spine, thus preserving the normal anatomical integrity of the spine. Other interbody device assemblies are also presently known. These include those disclosed in U.S. patent application Ser. No. 11/623,356, filed Jan. 16, 2007, titled “Minimally Invasive Interbody Device,” and Ser. No. 11/932,175, filed Oct. 31, 2007, titled “Minimally Invasive Interbody Device Assembly,” which are hereby incorporated by reference in their entirety.
Typically, the bone graft material is autogenous bone material taken from the patient, or allograft bone material harvested from a cadaver. Synthetic bone material can also be used as the graft material. Generally, the patient's own bone material offers the best fusion material since it offers osteoinductive, osteoconductive, and osteogenesis properties. Known bone fusion materials include iliac crest harvest from the patient, bone graft extenders, such as hydroxyapetite and demineralized bone matrix, and bone morphogenic protein.
Minimally invasive surgical procedures have been devised in an attempt to preserve normal anatomical structures during spinal surgery. Many known procedures for spinal fusion, however, still are more invasive than desired. Additionally, many known procedures do not provide the level of control over the delivery and placement of the bone graft material as could be desired. Additionally, current interbody devices only allow for a limited application of bone material (i.e., cages), and because of their relative size place the neural elements at risk during placement, often resulting in undersized implants being placed.
It is therefore one object of the present invention to provide a spinal implant system that reduces approach related morbidity, allows for more bone graft placement and/or provides improved control of the delivery and/or placement of bone graft material.